Single-Mode Polymer Ridge Waveguide Integration of Organic Thin-Film Laser

Abstract

Organic thin-film lasers (OLAS) are promising optical sources when it comes to flexibility and small-scale manufacturing. These properties are required especially for integrating organic thin-film lasers into single-mode waveguides. Optical sensors based on single-mode ridge waveguide systems, especially for Lab-on-a-chip (LoC) applications, usually need external laser sources, free-space optics, and coupling structures, which suffer from coupling losses and mechanical stabilization problems. In this paper, we report on the first successful integration of organic thin-film lasers directly into polymeric single-mode ridge waveguides forming a monolithic laser device for LoC applications. The integrated waveguide laser is achieved by three production steps: nanoimprint of Bragg gratings onto the waveguide cladding material EpoClad, UV-Lithography of the waveguide core material EpoCore, and thermal evaporation of the OLAS material Alq3:DCM2 on top of the single-mode waveguides and the Bragg grating area. Here, the laser light is analyzed out of the waveguide facet with optical spectroscopy presenting single-mode characteristics even with high pump energy densities. This kind of integrated waveguide laser is very suitable for photonic LoC applications based on intensity and interferometric sensors where single-mode operation is required.